1. Field of the Invention
The present invention relates to heating and air conditioning systems and air distribution terminals that are preferably incorporated into underfloor heating and air conditioning systems.
2. Description of the Related Art
There are a number of ways to heat and air condition spaces within buildings. In many office buildings heating and air conditioning is achieved through ducts and plenums in the ceilings of the buildings. While such systems are generally acceptable in many situations, these systems and the heating and cooling principles applied in such systems have drawbacks. By means of example only, because the cooling air is introduced from the ceiling, it forces some of the warmer air in the ceiling downward. and may mix with it. This results in cooling inefficiencies, reduction in ventilation effectiveness, and also tends to cause pollutants in the ceiling area to mix with air throughout the space being conditioned. Ceiling-based systems also are often expensive to install, since all of the required plenums, ducting, and terminals, among other things, must be placed in the ceilings. Moreover, it is difficult and time consuming to service such systems, after they are installed. Ceiling systems are also relatively difficult and expensive to modify or reconfigure, as circumstances require. For these and other reasons there has been a need for alternate heating and air conditioning systems, particularly for large facilities having one or many stories. This need has become more pronounced because buildings now often need to have the capacity to permit underfloor electrical wiring for power, computer, and telecommunication applications, applications that commonly need to be changed frequently after they are originally installed.
One alternative proposed system and method of heating and cooling buildings has been underfloor heating, ventilating, and air conditioning ("HVAC") systems in which the heating and/or cooling air is applied through openings in the floor. While such systems in theory have some benefits over other commercial systems, the underfloor systems and methods known to applicant have had a number of drawbacks that have significantly narrowed the acceptability of such systems to date. Primarily, existing underfloor systems generally provide a limited range of configurations, thus falling short of meeting varied, known operating conditions. This limited capability arises in part because these systems are generally designed to operate under constant volume. In addition, the floor air delivery devices that are known to applicant are simple grille devices that direct the air in a fixed pattern regardless of whether the pattern is suitable for the specific application. Such devices are pressure dependent devices that have an air velocity that is dependent upon the entering air pressure at the grille face. This produces another disadvantage--namely, at low flow, "puddling" of the more dense conditioned air may take place, which is very uncomfortable to the ankles and feet of the occupants. Yet another drawback results from the high cost to adequately cool different zones. For example, to provide temperature control, often these systems include a number of different zones that are separated by plenum dividers. In sum, the underfloor devices and systems known to the applicant are inflexible in construction, have high operating costs, and are generally intended to meet a limited range of air distribution conditions.
Another possible alternative would be to apply ceiling terminal ducting technology to floor systems. So far, this approach has been impractical and consequently has met with little success.